Method for fabricating metal electrode with atomic layer deposition (ALD) in semiconductor device

ABSTRACT

A method for fabricating a semiconductor memory device, includes the steps of loading a substrate into a reaction chamber for an atomic layer deposition, injecting an precursor consisting of M and X into the reaction chamber and including an adsorption precursor onto a surface of the substrate, wherein M is one of nickel (Ni), palladium (Pd) and platinum (Pt) and X is ligand, purging the reaction chamber, injecting a reaction gas into the reaction chamber and forming a metal layer by reacting the precursor adsorbed on the surface of the substrate with the, reaction gas and purging the reaction chamber.

FIELD OF THE INVENTION

[0001] The present invention relates to a method for fabricating a metalelectrode in a semiconductor device; and, more particularly, to a methodfor fabricating a metal electrode of nickel (Ni), palladium (Pd) orplatinum (Pt) with an atomic layer deposition (ALD) technique.

DESCRIPTION OF RELATED ART

[0002] When fabricating a metal electrode by using nickel, palladium orplatinum according to the prior art, the metal electrode is formed by achemical vapor deposition (CVD) technique using a precursor, of which anoxidation state is of +2 or +4, and a reactive gas, such as a hydrogengas or the like.

[0003] Generally, the CVD technique is employed for depositing a film onan exposed surface of a substrate, such as a silicon wafer or the like,and the precursor used at the CVD is a thermo-decomposable and volatilecompound. The precursor is contacted on a substrate heated over adecomposition temperature of the precursor. A film composed of metal,metal compound, metal alloy, ceramic, metal oxide and a mixture thereofis formed on a substrate, which depends on selection of precursor andreaction conditions.

[0004] A method for fabricating a metal electrode of nickel, palladiumor platinum by using CVD, hereinafter, will be described.

[0005] When the metal electrode is formed by CVD, a precursor (MX₂ orMX₄), of which an oxidation state is of +2 or +4, and a reaction gas,such as an oxygen gas, a hydrogen gas or the like, are used. In theprecursor MX₂ or MX₄, M is one of nickel, palladium and platinum and Xis an anionic ligand.

[0006] When the oxygen gas is used as the reaction gas, the oxygen gasreduces an oxidized metal precursor by a reaction with the metalprecursor and reacts with the anionic ligand X to generate by-products.The ligand is a material selected from the group consisting of H₂, Cl,Br, I, C₁˜C₁₀ alkyl, C₂˜C₁₀ alkenyl, C₁˜C₈ alkoxy, C₆˜C₁₂ aryl,β-diketonates, cyclopentadienyl, C₁˜C₈ alkylcyclopentadienyl andderivatives thereof including halogens therein. Neutral products amongthe reaction products, which are produced through oxidation andreduction reaction between the oxygen gas and the metal precursor, maybe removed with a vacuum pump. However, since it is very difficult toremove the anionic and cationic products, they may be left in the metalelectrode as impurities.

[0007] Also, The reaction of oxygen and the ligand is not only complex,but also rapidly performed, so that impurities such carbon, hydrogen andoxygen remain in the metal electrode. The remaining impurities arediffused at a post-thermal process so that a characteristic of the metalelectrode is degraded.

[0008] To solve the above problem, in case of using hydrogen, which is areductive gas, as a reaction gas, the metal electrode precursorpreviously undergoes decomposition and then a carbonate is produced sothat impurities still remain in the metal electrode because a depositiontemperature has to be set over 700· in order to activate the hydrogen.

[0009] When the metal electrode is used as an top electrode of acapacitor with dielectric layers such as Ta₂O₅, (Bi,La)₄Ti₃O₁₂ (BLT) ,SrBi₂Ta₂O₉ (SBT), Sr_(x)Bi_(y)(Ta_(i)Nb_(j))₂O₉ (SBTN),Ba_(x)Sr_((1−x))TiO₃ (BST), Pb(Zr,Ti)O₃ (PZT) and the like, if the H₂gas is supplied at a high temperature as a reaction gas, H₂ reduces thedielectric oxide layer so that the desired electrical characteristicscannot be obtained.

[0010] Furthermore, when the metal electrode is formed with nickel,palladium or platinum by using CVD, since the metal precursor of a gasstate and the reaction gas are simultaneously supplied into the reactionchamber, a decomposition reaction occurs between the reaction gas andthe metal precursor. Non-volatile materials, such as carbonate, oxideand the like, are also produced by the above reaction. Thesenon-volatile materials exist in the metal electrode and cause generationof particles, which induce an operation failure.

[0011] When a nickel metal electrode is formed by CVD, sizes of nickelparticles are about 0.1 □ to 1.0 □. If the particles having a size ofabout 0.1 □ to 1.0 □ stick to the dielectric layer formed to a thicknessof about 0.03 □, a serious problem is caused for a step coveragecharacteristic of the dielectric layer and a dielectric characteristicis deteriorated. In case of a memory device, since an operation failureof a memory cell having these particles is caused, so that the yield isdecreased.

SUMMARY OF THE INVENTION

[0012] It is, therefore, an object of the present invention to provide amethod for fabricating a metal electrode capable of removing impuritiesand particles therein by using an atomic layer deposition (ALD)technique.

[0013] In accordance with an aspect of the present invention, there isprovided a method for fabricating a semiconductor memory device,comprising the steps of: loading a substrate into a reaction chamber foran atomic layer deposition; injecting an precursor consisting of M and Xinto the reaction chamber and including an adsorption precursor onto asurface of the substrate, wherein M is one of nickel (Ni), palladium(Pd) and platinum (Pt) and X is ligand,; purging the reaction chamber;injecting a reaction gas into the reaction chamber and forming a metallayer by,reacting the precursor adsorbed on the surface of the substratewith the reaction gas; and purging the reaction chamber.

[0014] In accordance with another aspect of the present invention, thereis provided a semiconductor memory device comprising: a substrate: and ametal layer formed on the substrate by using an atomic layer deposition,wherein the metal layer is formed by reacting a precursor consisting ofM and X with a reaction gas on a surface of the substrate, wherein M isone of nickel (Ni), palladium (Pd) and platinum (pt), and X is ligand.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other objects and features of the instant inventionwill become apparent from the following description of preferredembodiments taken in conjunction with the accompanying drawings, inwhich:

[0016]FIGS. 1A to 1C are cross-sectional views illustrating an atomiclayer deposition (ALD) technique of a metal electrode in accordance withthe preferred embodiment of the present invention; and

[0017]FIG. 2 is a diagram illustrating a sequential injection cycle of ametal precursor, the reaction gas and the purge gas in accordance withthe preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, a method for fabricating a metal electrode by usingan atomic layer deposition (ALD) technique of a capacitor in accordancewith the present invention will be described in detail referring to theaccompanying drawings.

[0019]FIGS. 1A to 1C are cross-sectional views illustrating an atomiclayer deposition (ALD) technique of a metal electrode in accordance withthe preferred embodiment of the present invention.

[0020] Hydrazine (N₂H₄) used as a reaction gas in accordance with thepreferred embodiment of the present invention forms a layer for a metalelectrode and neutral by-products such as HX, NH₃ and N₂. Since theby-products have a high volatility, they can be easily removed by usinga vacuum pump.

[0021] Hydrazine is a compound of nitrogen and hydrogen. Hydrazinesmokes in air and is a transparent liquid. Also, hydrazine smells likeammonia and has a melting point, boiling point and specific gravity of2·, 113.5· and 1.011, respectively.

[0022] The reaction between the metal precursor, of which oxidationstate is +2 and the hydrazine is as a following equation 1:

MX₂+2N₂H₄→M+2HX+2NH₃+N₂   (1)

[0023] Herein, M is the metal selected from a group consisting of one ofnickel, palladium and platinum, and X is the ligand selected from thegroup consisting of H, F, Cl, Br, I, C₁˜C₁₀ alkyl, C₂˜C₁₀ alkenyl, C₁˜C₈alkoxy, C₆˜C₁₂ aryl, diketonates, cyclopentaienyl, C₁˜C₈alkylcyclopentadienyl and derivatives thereof including halogenstherein.

[0024] As mentioned above equation 1, a layer consisting of the metal(M) is deposited by the reaction of hydrazine N₂H₄ and the metalprecursor (MX₂) and some reaction products (HX, 2NH₃, N₂) having a highvolatility are produced. At this time, HX, which is a compound of thehydrogen and ligand, can be easily removed by a vacuum pump.

[0025] In the preferred embodiment, when a layer for metal electrode isdeposited according to the above equation 1 with an atomic layerdeposition (ALD) technique. A reaction can be controlled more easily ina molecular level by the ALD technique compared to a CVD technique.

[0026] Generally, one period for forming a layer for metal electrodewith ALD is follows. A source gas is supplied to a chamber for the ALDand one layer of the source gas is chemically adsorbed onto a surface ofa substrate. Thereafter, a non-reacted source gas, which is physicallyadsorbed, is purged by providing a purge gas. Subsequently, a reactiongas is injected into the chamber to reaction with the layer of sourceadsorbed onto the surface of the substrate, so that a desired layer isdeposited and the remaining reaction gas is removed by proving a purgegas. Thus, one period is completed.

[0027] As described in the above, the ALD technique uses a surfacereaction mechanism so that a stable and uniform thin layer can beacquired. Also, because the source gas and the reaction gas areseparately and sequentially injected and purged, particle production,which is caused by a gas phase reaction, can be suppressed.

[0028]FIGS. 1A to 1C are cross-sectional views illustrating the metalelectrode deposition by using the ALD technique in accordance with thepreferred embodiment of the present invention.

[0029] As shown in FIG. 1A, a substrate 1, which the metal electrodewill be deposited, is loaded into a reaction chamber (not shown) and thesubstrate 1 is preheated to a temperature ranging from about 100· to700·. When the hydrazine is used as the reaction gas, a reaction can beactivated below temperature of about 500·. Therefore, in case ofapplying the metal, the method in accordance with the present inventionto for a top electrode formed on the dielectric layer of a capacitor,reduction of the dielectric layer is prevented so that a characteristicof the dielectric layer can be maintained.

[0030] After preheating the substrate 1, the vaporized metal precursor2, i.e., a source gas, is injected into the reaction chamber with acarrier gas such as Ar, N₂ or the like, so that the metal precursor 2 isadsorbed on a surface of the preheated substrate 1. Subsequently, theinjection of the metal precursor gas is stopped and a purge gas, such asN₂, He, Ar or a mixture gas thereof, is injected into the chamber, andby-products, such as a non-adsorbed metal precursor and the like, areremoved by using a vacuum pump.

[0031] As shown in FIG. 1B, hydrazine 4, which is a reaction gas, isinjected and reacted with the metal precursor 3 adsorbed on the surfaceof the substrate 1, so that a metal layer 5 is formed. At this time,by-products, such as HX, NH₃ and N₂, are produced as shown in equation1.

[0032] In accordance with the preferred embodiment of the presentinvention, hydrazine (N₂H₄), NR₃, C₁˜C₁₀ alkylhydrazine, C₁˜C₁₀dialkylhydrazine, NH₃, NH₂R, NHR₂ or a mixture gas thereof is used asthe reaction gas. Herein, “R” denotes a material selected from the groupconsisting of hydrogen, C₁˜C₁₀ alkyl, C₂˜C₁₀ alkenyl, C₁˜C₈ alkoxy,C₆˜C₁₂ aryl and derivatives including elements of halogen group therein.

[0033] Next, the reaction gas injection is stopped, and a purge gas,such as N₂, He, Ar or a mixture gas thereof, is injected into thechamber to remove the reaction by-products (HX, NH₃, N₂) and anon-reacted reaction gas.

[0034] The above procedure as one cycle is repeatedly carried out sothat the metal electrode 6 consisting of a number of the metal layer 5is obtained as shown in FIG. 1C.

[0035]FIG. 2 is a diagram illustrating each injection cycle of the metalprecursor, the reaction gas and the purge gas according to thedeposition time. One cycle consists sequential injections of the metalprecursor, the purge gas, the reaction gas and the purge gas. As thecycles are repeatedly performed, the metal electrode can be formed to adesired thickness.

[0036] The metal electrode of nickel, palladium or platinum formed bythe above ALD technique may be applied to a gate electrode, bit line oran electrode of a capacitor in a semiconductor memory device.

[0037] As the method fabricating the metal electrode in accordance withthe preferred embodiment of the present invention is applied, impuritiesin the metal electrode can be minimized. As shown in equation 1, sincethe by-products produced by the reaction between the metal precursor andthe reaction gas are neutral products having a high evaporationpressure, by-reaction products can be easily removed from the reactionchamber by a vacuum pump. Therefore, impurities are not nearly left inthe metal electrode.

[0038] In the conventional chemical vapor deposition technique, thereaction gas and the metal precursor, are reacted so that non-volatilereaction products are produced. However, the reaction between thereaction gas and the precursor is performed only on the surface of thesubstrate according to the present invention so that particles are notproduced.

[0039] Accordingly, when the metal electrode of nickel, palladium orplatinum is formed in accordance with present invention, a pure metalelectrode can be obtained and a problem due to particle generation canbe solved, so that reliability and yield of the device can be increased.

[0040] While the present invention has been described with respect tothe particular embodiments, it will be apparent to those skilled in theart that various changes and modifications may be made without departingfrom the spirit and scope of the invention as defined in the followingclaims.

What is claimed is:
 1. A method for fabricating a semiconductor memorydevice, comprising the steps of: loading a substrate into a reactionchamber for an atomic layer deposition; injecting an precursorconsisting of M and X into the reaction chamber and including anadsorption precursor onto a surface of the substrate, wherein M is oneof nickel (Ni), palladium (Pd) and platinum (Pt) and X is ligand;purging the reaction chamber; injecting a reaction gas into the reactionchamber and forming a metal layer by reacting the precursor adsorbed onthe surface of the substrate with the reaction gas; and purging thereaction chamber.
 2. The method as recited in claim 1, wherein theprecursor is MX₂ or MX₄.
 3. The method as recited in claim 2, furthercomprising the step of preheating the substrate at a temperature ofabout 100· to 700· before injecting the precursor.
 4. The method asrecited in claim 2, wherein the ligand is a material selected from thegroup consisting of H₂, Cl, Br, I, C₁˜C₁₀ alkyl, C₂˜C₁₀ alkenyl, C₁˜C₈alkoxy, C₆˜C₁₂ aryl, β-diketonates, cyclopentadienyl, C₁˜C₈alkylcyclopentadienyl and derivatives thereof including halogenstherein.
 5. The method as recited in claim 2, wherein a purge gasselected from a group consisting of N₂, He, Ne, Ar and a mixture gasthereof is injected at the step of purging the reaction chamber.
 6. Themethod as recited in claim 2, wherein the reaction gas is a gas selectedfrom the group consisting of NH₃, hydrazine, C₁˜C₁₀ alkylhydrazine,C₁˜C₁₀ dialkylhydrazine and a mixture gas thereof.
 7. The method asrecited in claim 2, wherein the reaction gas is a gas selected from thegroup consisting of NH₂R, NHR₂, NR₃ and a mixture gas thereof and R is amaterial selected from the group consisting of H, C₁˜C₁₀ alkyl, C₂˜C₁₀alkenyl, C₁˜C₈ alkoxy, C₆˜C₁₂ aryl and derivatives thereof including oneor more halogen groups.
 8. The method as recited in claim 2, wherein anAr gas or an N₂ gas is used as a carrier gas at the step of injectingthe precursor for carrying the precursor into the reaction chamber. 9.The method as recited in claim 2, wherein the metal electrode is one ofa gate electrode, bitline and an electrode of a capacitor.
 10. Asemiconductor memory device comprising: a substrate: and a metal layerformed on the substrate by using an atomic layer deposition, wherein themetal layer is formed by reacting a precursor consisting of M and X witha reaction gas on a surface of the substrate, wherein M is one of nickel(Ni), palladium (Pd) and platinum (pt), and X is ligand.
 11. Thesemiconductor memory device as recited in claim 10, wherein theprecursor is MX₂ or MX₄.
 12. The semiconductor memory device as recitedin claim 11, wherein the ligand is a material selected from the groupconsisting of H₂, Cl, Br, I, C₁˜C₁₀ alkyl, C₂˜C₁₀ alkenyl, C₁˜C₈ alkoxy,C₆˜C₁₂ aryl, β-diketonates, cyclopentadienyl, C₁˜C₈alkylcyclopentadienyl and derivatives thereof including halogenstherein.
 13. The semiconductor memory device as recited in claim 11,wherein the reaction gas is a gas selected from the group consisting ofNH₃, hydrazine, C₁˜C₁₀ alkylhydrazine, C₂˜C₁₀ dialkylhydrazine and amixture gas thereof.
 14. The semiconductor memory device as recited inclaim 11, wherein the reaction gas is a gas selected from the groupconsisting of NH₂R, NHR₂, NR₃ and a mixture gas thereof and R is amaterial selected from the group consisting of H, C₁˜C¹⁰ alkyl, C₂˜C₁₀alkenyl, C₁˜C₈ alkoxy, C₆˜C₁₂ aryl and derivatives thereof including oneor more halogen groups.